Presently, electrical resistors are formed in semiconductor devices by forming elements of conductive material with neck portions of reduced cross-section and/or volume The reduced cross-section/volume of the neck portion increases the electrical resistance of the resistor element by reducing the amount of material through which electrical current must pass.
Semiconductor electrical resistor elements are conventionally made by forming a strip of conductive material horizontally or vertically over the semiconductor substrate, and then trimming a portion of the strip using laser ablation to form a neck portion of known and reduced cross-section area. The resulting electrical resistance of the conductive element will be a function of the conductivity of the material used to form the element, and the physical dimensions of the neck portion.
One drawback to the conventional formation of semiconductor electrical resistors is that it can be difficult to accurately form the neck portions with the desired dimensions for certain devices. Deviations in neck portion cross-sectional size can not only drastically change the intended electrical performance of these resistors, but can also cause the devices in which they are contained to fail. For example, semiconductor electrical resistors are used to operate (program, read, erase) memory cell arrays. In order for a memory cell array to properly work, the electrical performance of each memory cell must be comparable, so that when the memory cells are read only those that have been programmed will be identified as such. However, since such arrays can contain millions of memory cells, and the physical dimensions of the memory cells are constantly shrinking, it can be extremely difficult to ensure that resistors throughout the array all have the precise desired neck portion dimensions.
There is a need for a improved technique for forming semiconductor resistors.